The present application relates to a sensor apparatus for detecting, for example, a press operation made by a user, and to a display apparatus including the sensor apparatus.
In recent years, portable information processing apparatuses typified by cellular phones are being made multifunctional, and the structure in which a display unit provided to a casing is caused to function as a user interface is proposed. For example, Japanese Patent Application Laid-open No. 2009-134473 discloses an electronic apparatus including a touch panel for detecting an input operation position on a display unit, and a press detection sensor for detecting an input operation force as a change in electric resistance between electrodes. Further, Japanese Patent Application Laid-open No. Hei 10-198503 discloses a force detecting touch pad for detecting a press to a touch surface as a change in electric capacitance between electrodes.
Generally, a sensor for detecting a capacitance change due to a press adopts a technique of changing a capacitance between electrodes while using the structure in which a distance between electrodes is variable by a press. Since a capacitance is changed in inverse proportion to a distance between electrodes, in a case where a distance between electrodes is reduced by a press by 2%, for example, a capacitance between electrodes is increased by about 2%. On the other hand, in a case where a capacitance value of a capacitive sensor itself is difficult to be increased because of restrictions of a driver circuit, a detection speed, and the like, the sensor capacitance is restricted to about several pF to several tens of pF in many cases, though depending on a system of a detection circuit. Therefore, in a case where a change in distance between electrodes is minute, for example, about 2%, a capacitance change between electrodes is also minute and therefore it is extremely difficult to ensure detection sensitivity.